Constitutive modeling of steel fiber-reinforced concrete

Experimental studies within the previous years showed that the behavior of concrete is improved by adding steel fibers. Due to bridging effect, steel fibers in a concrete matrix prevent crack propagation under static loads. This phenomenon increases the load-bearing capacity of steel fiber-reinforced concrete, specifically after the peak load. In contrast to similar studies, in this study the effect of fibers on steel fiber-reinforced concrete is directly described based on uniaxial compressive and tensile stress–strain curves. For this purpose, the effect of fiber on the stress variations is extracted from the difference between steel fiber-reinforced concrete and its corresponding concrete matrix uniaxial stress–strain curves. These differential stress curves were extracted from 103 experimental specimens, collected from the literature. Then, some equations were developed for them with appropriate accuracy, using genetic programming technique. These equations were only based on primary specifications of fibers and concrete matrix. In the next stage, an elastoplastic damage constitutive model initially developed for plain concrete was modified, using the developed steel fiber-reinforced concrete modeling equations. The proposed model was implemented in a finite element analysis software and successfully simulated the steel fiber-reinforced concrete behavior subjected to uniaxial and flexural experiments.